The cnc machining optical parts is divided into thermal processing, cold processing and special processing. Thermal processing is currently mostly used in the preparation of blanks for optical parts;
Cold working is sawing, rough grinding, fine grinding, polishing and centering edging with loose or fixed abrasives.
Special processing only changes the performance of the polished surface, but does not change the shape and size of the optical parts, which includes coating, scale, photography and gluing. The main tasks of each process of cold working are:
- Rough grinding (cutting) process: it is to make the parts have basically accurate geometry and size.
- Fine grinding (coarse grinding) process: it is to process the parts to the specified size and requirements, and prepare for polishing.
- Polishing (fine grinding) process: it is to make the surface of the part bright and achieve the required optical precision.
- Centering process: the outer circle of the lens is processed relative to the optical axis.
- Gluing process: it is to glue different optical parts together so that the optical axes coincide or turn in a certain direction.
The three basic processes of the current processing technology of spherical optical parts are:
- 1. Milling (cutting) based on the principle of Fancheng method
- 2. High-speed coarse grinding based on the principle of pressure transfer
- 3. High-speed polishing based on the principle of pressure transfer.
Although the milling (cutting) of the Fancheng method has high processing efficiency, there are many factors that affect the error, and it is difficult to achieve high precision and roughness. The quasi-spherical high-speed rough grinding and high-speed polishing based on the principle of pressure transfer, the force on the parts is more uniform, and the processing efficiency is also high. However, the surface shape of the grinding (mold) tool must be accurately trimmed in advance to ensure the surface shape accuracy of the parts. Accurate trimming of the surface shape accuracy requires the experience and skills of the operator, and repeated trimming is required.
Characteristics of traditional grinding and high-speed grinding
1. Traditional grinding
Traditional grinding, also known as classical grinding, is a processing method with a long history
Its main features are:
- Use ordinary grinding machine or manual operation;
- Requires high technical level of personnel;
- The abrasive material mostly uses loose sand (grinding sand) to polish asphalt
- The polishing agent is cerium oxide or iron oxide;
- The pressure is realized by adding a load. Although this method is inefficient, it is still used because of its high machining accuracy.
2. High-speed grinding and polishing
Generally refers to quasi-sphere method (or arc swing method).
Its main features are:
- Using high speed, high pressure and more effective use of polishing molds, greatly improving the polishing efficiency
- The pressure head swings in an arc around the center of the ball, and the working pressure always points to the center of the ball, which is also shaped by the ball mold.
3. Fan Chengfa
The quasi-spherical method has lower requirements on the accuracy of the machine tool, and the processing method is similar to the traditional method, which is easy to implement and widely used; the Fancheng method has higher requirements on the accuracy and adjustment of the machine tool, and is rarely used at present.
Comparison between quasi-sphere center method and traditional method
1. Quasi-sphere method
The polishing mold (or mirror disk) swings in an arc around the center of curvature of the mirror disk (or polishing mold), and the pressure direction is always aligned with the center of the sphere, so the mirror disk bears constant pressure, which creates conditions for uniform polishing.
2. Traditional law
It is a plane swing, and the heavy pressure block is pressed vertically, and its pressure changes with the swing angle, so it is easy to cause uneven polishing. Pressurization adopts spring or air pressure, and the force is relatively constant and stable. However, the traditional grinding and polishing method uses heavy pressure blocks to pressurize, which has a large volume and large vibration.
3. Considerations of spherical grinding for mirror discs
- The opening angle of the mirror disk should not be too large to facilitate the stability of the aperture. In a multi-row mirror disk, the opening angle should not be greater than 140°; for a disk with three lenses, if it exceeds 140°, it will not affect much.
- The elastic upper plate can withstand the high speed and high pressure in high-speed grinding, but the mirror plate must be installed correctly.
- 1. The axial positioning datum of the rubber ball mold must comply with the datum plane for cutting and rough grinding thickness control and the datum plane required for the center of the ball in high-speed grinding (if the mirror disc is installed on the main shaft)
- 2. The axis of the seat (positioning hole) coincides with the normal of the spherical surface and has the same depth;
- 3. The radius of curvature and the radius of curvature of the surface to be bonded should be reasonable
- 4. The relative size between the seat (positioning hole) and the axial reference plane of the rubber ball mold is consistent, and there is an air elimination hole.
- 5. Adhesive degree is sufficient; bonding area is sufficient; bonding temperature is appropriate.
Requirements for cutting process
First, the shape of the cut spherical surface must be regular, and the radius of curvature must meet the tolerance range specified by the process;
Second, the surface roughness should meet the requirements of coarse grinding;
The third is to remove a certain margin to ensure that the impurity layer of the blank is removed.
If the passing rate of the lens decreases after polishing, checking the surface accuracy of the cutting surface may find the crux of the problem.
1. Precision of cutting equipment
- Workpiece shaft full runout: 3um
- Grinding wheel shaft full runout: 3um
- Workpiece axis generatrix accuracy: 1um
- Workpiece axis movement accuracy: 3um
- Equiaxiality of workpiece and grinding wheel shaft surface: 1um
For the spherical surface, neither asphericity nor super chrysanthemum pattern and deep fragmentation layer will be produced on the same surface.
Rough grinding process requirements
It is extremely important to obtain a reasonable coarse grinding surface structure for fine grinding, which directly affects the efficiency of fine grinding and its processing quality. The nature of the rough ground surface can be characterized by macroscopic and microscopic surface irregularities.
The macroscopic irregularities are caused by the deviation of the grinding tool during the grinding process, and the macroscopic irregularities can be greatly reduced by choosing the appropriate polishing die material in the fine grinding.
Microscopic irregularities are determined by the nature of glass grinding.
1. Effect of surface structure on fine grinding process
The efficiency of the polishing process depends on the properties of the concave-convex layer and the crack layer left after glass grinding. The general misconception is that the smaller the uneven layer on the rough grinding surface during polishing, the better, which ignores the effect of the microstructure of the rough grinding surface on the polishing process. Polishing molds, especially thermosetting plastic molds, are easy to passivate and lose polishing ability during the polishing process. The concave-convex layer is beneficial to reduce or eliminate this passivation phenomenon.
The polishing process can basically be divided into two stages, the first stage removes the uneven layer, and the second stage removes the crack layer.
At the beginning of the first stage, the polishing mold is in contact with the top of the concave-convex layer of the glass, and the pressure is very high, and the valleys provide good conditions for the polishing liquid to enter the entire surface, so the polishing is very fast. As the polishing process continues, the contact area increases, the pressure decreases, and the adhesion of the polishing fluid decreases, slowing down the polishing process.
When the polishing surface reaches the crack layer, the glass surface is in full contact with the surface of the polishing mold, and the polishing process tends to be stable and slow, while the polishing mold begins to passivate, the polishing continues, the passivation intensifies, and the polishing efficiency further decreases. The degree of passivation depends on the duration of the process, which is directly determined by the depth of the crack layer.
The optimal value of the thickness of the concave-convex layer is mainly determined by the properties of the polishing mold material and the polishing agent used in conjunction with this material. Other factors include the spindle speed, pressure and the ability to enter the polishing solution.
Using different coarse grinding methods, or in the same method, the crack layer obtained is different with the degree of passivation of the abrasive tool and the state of cooling and lubrication. Practice has proved that although the workpiece processed by passivated diamond abrasive tools has a small concave-convex layer, the crack layer is very deep.
Therefore, not only the influence of the concave-convex layer on polishing must be considered, but also the depth of the crack layer should be considered as an important indicator of the rough grinding process.
How to maintain the accuracy of the radius of curvature of the surface of the coarse grinding dish?
Coarse grinding is carried out by contacting the grinding plate with the lens surface. Although the radius of curvature of the surface of the grinding dish is modified very well at the beginning of use, as the lens is ground, the grinding dish is also constantly worn, and gradually the processing accuracy of the lens cannot be guaranteed.
To keep the radius of curvature of the coarse grinding dish constant or less, you should take:
1. Reasonable selection of tools
All the upper fixtures are always smaller than the lower fixtures because the upper fixtures need to swing.
If the size of the upper jig is the same as that of the lower jig, there are too few opportunities for edge grinding of the upper jig, and the upper jig tends to warp.
If the size of the upper jig is much smaller than the size of the lower jig, exceeding the specified data, the edge of the upper jig will not be exposed during the swing process, the edge of the upper jig will be worn too much, and the upper jig will have a collapsed edge the trend of.
If the size of the upper jig is larger than that of the lower jig, then when swinging, the chances of the edge of the lower jig to be exposed will be too small, the edge of the lower jig will be worn too much, and the lower jig will tend to collapse.
The skills of grinding dishes
When repairing a concave grinding dish, the lens aperture is thin (negative), so the center part of the concave grinding dish should be ground more. If the convex and concave are repaired, the convex should be on the bottom and the concave on the top, and the swing should be large, about 1/2 of the concave grinding. If the lens aperture is thick (polarized), the concave edge of the grinding dish should be ground more.
If the convex and concave are repaired, the concave should be on the bottom and the convex on the top, and the swing should be large, about 1/3 of the convex grinding.
When repairing a convex grinding dish, the lens aperture is thin (negative), so the edge of the concave grinding dish should be ground more. If the convex and concave are repaired, the convex should be on the bottom and the concave on the top, and the swing should be large, about 1/2 of the concave grinding.
If the lens aperture is thick (polarized), the center part of the convex grinding dish should be ground more. If the convex and concave are repaired, the concave should be on the bottom and the convex on the top, and the swing should be large, about 1/3 of the convex grinding. 10°, right swing 40°.
Factors Affecting Polishing
The quality of polishing results is influenced by many factors:
- workpiece roughness
- air temperature and relative humidity
- Air dust content
- glass type
- The size ratio of parts and fixtures
- The nature of the polishing agent
- Working shaft speed
- Swing frequency, swing amplitude and swing center position
- The temperature and pressure of the polishing surface
- Input amount and temperature of polishing agent
The influence of polishing agent (grinding powder)
Abrasive powder has different effects on different types of optical materials, or optical parts with the same optical material but different surface quality requirements.
The different production methods and different processes of grinding powder, as well as its physical properties, have a great influence on the grinding efficiency. Different production methods of iron oxide have different crystal structures and different grinding capabilities; different production methods of cerium oxide, The grinding efficiency is different. The grinding powder obtained by the same production method has a higher grinding ability after the firing process than that without the firing process.
The hardness of the grinding powder particles should be compatible with the hardness of the glass, the hardness of the grinding skin, and the grinding pressure. Too much hardness will cause scratches on the glass surface, and too low hardness will reduce the grinding efficiency.
(1) Concentration of grinding liquid
For iron oxide (red powder) grinding fluid, the weight ratio of iron oxide to water is 1:3 ~ 1:4.
For cerium oxide (yellow powder, white powder) grinding liquid,
The weight ratio of cerium oxide to water is 1:5 or slightly dilute.
The concentration of the grinding liquid does not match the ideal value, which will lead to a decrease in grinding efficiency.
When the concentration is too high, the grinding efficiency will decrease instead, because the amount of water is insufficient, which makes it difficult to dissipate heat.
Excessive grinding dust accumulates on the glass surface, and the grinding pressure cannot effectively function.
When the concentration is too low, the surface temperature drops, and the micro-cutting action is reduced at the same time.
(2) Supply amount of grinding liquid
Under certain process conditions, the amount of grinding fluid needed to maximize the grinding efficiency is a moderate amount of grinding fluid. Maintain a moderate supply of grinding fluid during grinding.
Polishing fluid parameters
If the liquid temperature is low, it is easy to cause scratches, and if it is too high, it is easy to deform the polishing layer. Generally, it is controlled between 30~38°C, the flow rate is 900~1000L/min, and the pH value is 3~9.
If the amount of grinding fluid supplied is too small, it is not conducive to mechanical grinding and heat dissipation; when the amount of grinding fluid supplied is too large, the surface temperature will drop, which is not conducive to chemical interaction, and at the same time, the fit will be deteriorated.
(3) PH value of the grinding liquid
Different types of optical glass have different requirements on the pH value of the grinding liquid. Generally, the iron oxide grinding liquid is neutral (PH=7); the cerium oxide grinding liquid is slightly acidic (PH=6~6.5) and it is easy to use.
In optical polishing, substances added to the polishing liquid that can change the performance of the polishing process are called additives. Those that stabilize the glass and reduce its susceptibility to corrosion, thereby further improving the quality of the optical surface, are called stabilizers.
Additives that can improve grinding efficiency and improve optical surface quality for iron oxide grinding fluid:
Zinc nitrate [Zn(NO3)2], zinc sulfate [ZNSO4], nickel chloride [NICL3], ferric chloride [FECL3], etc.
Additives that can increase the grinding rate and improve the quality of optical surfaces for cerium oxide slurries:
Cerium ammonium nitrate [(NH4)2CE(NO3)6], zinc sulfate [ZNSO4].
The addition amount of additives is not arbitrary, and each additive has its ideal addition amount for different grades of polishing powder and different types of optical glass.
Factors Affecting Surface Finish
There are blisters on the edge of the lens. One reason is that the aperture is high (positive) after fine grinding. When the center is polished, there are blisters on the edge. In addition, when the lens “walks”, it will also cause blisters on the edge. There are blisters in the middle of the lens. Another reason is that the aperture is too low after fine grinding, the edges have been polished and the center has not been polished, and the “moving” of the lens may also cause blisters in the middle of the lens. Coarse blisters on the lens surface are often caused by insufficient fine grinding.
During the polishing process, sometimes there will be something like oil spots on the surface of the lens, which is related to the chemical stability of the glass, the performance of the polishing powder, and the matching of the polishing mold. It can be eliminated by adding a small amount of zinc sulfate to the polishing powder suspension (about 6 grams per liter).
When using the original device (sample) to inspect the lens surface aperture, if the original device (sample) and the lens surface are not cleaned carefully, the lens surface will be easily damaged.
Grinding leather and selection
Polishing mold: Polyurethane (polyurethane), divided into polyether type and polyester type according to different raw materials used. However, when the ingredients and molding process are slightly deviated, the performance difference is very large.
Grinding leather (polishing mold)
Because different polyurethane polishing materials have different water absorption properties, the time to reach water absorption balance varies greatly. Therefore, before repairing the mold, the polishing mold should be soaked in the polishing solution, and then repair the mold after reaching the water absorption balance. Otherwise, the polishing mold will be damaged. Surface shape changes; after use, it should be soaked in polishing solution, otherwise, due to water evaporation, the surface shape will change, and the fit of the polished mold lens will be reduced when it is used again. The polyurethane polishing mold must match the grade of optical glass and the specification of cerium oxide grinding powder.
The choice of polishing die
- 1. If it is too thick, the hardness is too small, it is easy to deform, and the processed parts are easy to collapse;
- 2. If it is too thin, the matching between the polishing mold and the lens is not good, and the surface of the part is easy to be scratched.
Traditional processing requirements
The choice of polishing glue
The hardness of the polishing glue is very important to the smooth progress of the polishing work. When the pressure per unit area is high, the speed is fast, and the room temperature is high, the polishing glue should be harder; on the contrary, it should be softer. The polishing glue used for polishing mirror disks with large diameters should be softer.
Whether the hardness of the polishing glue is suitable can be determined according to the surface condition of the polished mold layer after polishing for a period of time. Under glancing light, when the surface of the polished mold layer is slightly shiny, and the color of the glue layer is similar to that of the polishing powder, the hardness is more suitable; when the surface of the polished mold layer is hairy, the glue layer is too hard; when the surface of the polished mold layer is shiny When it is oily asphalt color, the adhesive layer is too soft.
Another way: use a knife to draw shallow grooves on the surface of the polished mold layer. When the polishing glue is too soft, the shallow grooves will be ground quickly.
Calculation of the number of postings per circle:
an: the number of workpieces on the nth circle
A: It is the number of workpieces in the innermost circle, which is generally 3 or 4 or 1
R: is a constant 6, that is, the number of pieces per circle (6≈2π)
N: which lap
Post 9 circles, 51 lenses can be pasted on the 9th circle
Overall post count calculation:
D: is the diameter of the fixture
d: Add 2mm to the diameter of the part
Sn is the total number of parts in each ring
S9=9*3+6/2*9*(9-1) → 3*1442/4*(6+2)2
Lens diameter is 6mm;
Fixture diameter is 144㎜;
Post 9 circles totaling 243pcs
Calculation of post volume;
d>1·179R can only be a single piece
1.035R≤d≤1·179R can be three pieces
d<1.035R can be four pieces
The smaller the D/R ratio, the easier it is to use more pieces.
0.7＜d/R＜0.78 6 pieces, 1 out of 5
0.66 ＜d/R＜0.7 seven, six
0.6＜d/R＜0.66 eleven pieces, three inside and eight outside
0.55<d/R<0.6 thirteen pieces, four inside and nine outside
When using α. =arcSin(b/2R) indicates that the half angle is above 30°,
b represents half of the caliber of the part α. half angle
R represents the radius of curvature of the part to be processed
At this time, according to experience, parameters such as the comparison of the diameter of the convex and concave grinding dishes, the deflection angle of the grinding dish, the relative speed of the grinding dish and the part, and the grinding pressure are set.
If the reference value of the concave type is greater than the design value △H, take the negative and take the positive
If the reference value of the convex shape is greater than the design value △H, take positive and negative
R is the radius of curvature, D is the diameter,
Calculation and development of new models of curvature radius, edge thickness difference, etc. can be referred to
△H is the height or depth of the spherical crown
One concave and one convex TC+△H1-△H2
Double concave TC+△H1+△H2
(△H1 is the depth of R1 surface) (△H2 is the depth of R2 surface) (TC is the center thickness)
Calculation of original device value (number of aperture bars) and graphic design value:
R△=N*0.00055*(2R/D)2 N : Number of apertures
R: standard design value (radius of curvature)
D: The original device is the effective diameter (the lens is the diameter of the blank, and the centering is the effective diameter of the finished product)
R△: tolerance value
Cutting angle formula:
Sina=D/（2*(R±r) ）? D=2 Sina(R±r)
D: The diameter of the whetstone
R: radius of curvature of the part
a: Angle of inclination of the whetstone
Generally, the inclination angle can be selected between 35° and 43°
r: end arc radius of whetstone
The relationship between the caliber (diameter) of the flat grinding dish and the caliber (diameter) of the mirror disc (the grinding dish is at the bottom) is Dm=(1.1～1.3)Dj;
When the value of Dm/Dj is larger, the grinding amount per unit time is larger, and vice versa.
When Dm/Dj and other process factors are constant, the larger the swing, the larger the grinding amount per unit time.
In order to ensure uniform grinding, Dm/Dj must be well matched with the swing amplitude, that is, when Dm/Dj is large, the swing amplitude must be large, and vice versa.
Coarse grinding dish coverage ratio calculation:
P=Z ×(?/2)2×π/(2πRH)P=Z ?2/(8RH)
: Diamond diameter
H: Height of spherical crown
R: diamond radius of curvature
Machine tool selection
There are many types of traditional grinding and polishing machine tools in different forms. Such as S12, M8, UDA6, S6, S4 and two dish repairing machines, (Giyan) pedal dish repairing machine.
Spherical center grinding machine, such as LP330, SSP6, MF2, light-in and imitation light-in machines.
For traditional grinding and polishing machine tools, the speed is not higher than 1800 rpm, and the general speed is 700-900 rpm; for spherical center grinding machines, the speed is 1800-3000 rpm.
When choosing a machine tool for machining(include cnc milling,cnc turning and more,China Be-Cu prototype is quality swiss machining companies) flat mirror disks, the processing range of general machine tools is the main focus, and less consideration is given to the size of the flat mirror disk. When selecting a machine tool for processing a spherical mirror disk, the processing range of the machine tool and the size of the spherical mirror disk should be considered.
Because the large spherical mirror disk needs slower rotating speed, swing speed, larger swing amplitude and higher power, while the small mirror disk is the opposite. Therefore, the corresponding machine tool should be selected for processing spherical mirror disks of different sizes.
Adjustment of the machine tool
When the lens height loss is 0.85R or hemisphere, the declination angle is 15°, and the swing range is 40°-50°, that is, the left swing is 5°-10°, and the right swing is 35°-40°.
Quasi-spherical machine tool:
- (1) According to the radius of the spherical surface of the workpiece, match the joint (or jig) of the corresponding height so that the center of the ball coincides with the center of the pendulum. If the center of the ball is not allowed to swing, the pressure will be uneven and the aperture will be difficult to control.One is the deflection angle of the rack;The second is the swing of the shelf.The choice of these two factors has a great influence on the aperture.
- (2) Loosen the nut of the eccentric disc (swing part), adjust the swing range of the swing frame, and tighten the nut when it is suitable.
- (3) When changing the swing position of the swing frame, loosen the auxiliary locking handles (nuts) of the swing frame, adjust the swing frame to the required angle, and then tighten the handles (nuts).
Correctly adjust the swing is one of the important factors to control the aperture.For hemispherical or super hemispherical lenses, it is generally desirable to have a deflection angle of 15° and a swing of 50°, that is, a left swing of 10° and a right swing of 40° are more appropriate.
- 1. Check the quasi-sphere center degree when the arc swings, and the polishing liquid in the cylinder should not be less than 3/4 of the cylinder volume;
- 2. Adjust the temperature of the polishing liquid and check whether it is unimpeded;
- 3. Press the switch, observe the operation of the machine tool, adjust the polishing time and the flow rate of the polishing liquid, and drive the empty car for 1 minute;
- 4. Adjust the spindle speed, swing arm swing, swing speed, pressure, and then correct it according to the quality during the polishing process. At the same time, the polishing mold should be repaired and scraped as needed, and the polishing liquid should be replaced according to the batch size to keep the polishing liquid clean.
Machine Tool Adjustment
Install the workpiece and mold, and adjust the length of the grinding rod to achieve the required pressure.
Traditional grinding and polishing machine tools:
- (1) With the machine tool spindle as the origin, when the grinding rod is moved to the outside of the spindle (closer to the operator) and to the inside, the distance between it and the spindle can be increased. However, when the grinding rod is moved to the outside of the main shaft, the arc distance of the upper frame swing is increased, and the aperture change speed is faster than when it is moved to the inside.
- (2) From the perspective of the normal force component, it should be light when changing the high aperture, and heavy when changing the low aperture.
Whether the adjustment of the machine tool is correct is the main factor affecting the instability of the aperture.
Machine tool adjustment includes: speed, pressure, relative speed of mirror and tool, relative displacement, etc.
The size of the swing (for top swing machine tools)
The larger the swing, the more the middle part of the upper jig and the edge of the lower jig will be worn, so the size of the swing should be appropriate. For the ball mold, the swing angle of the upper jig is about 0.4-0.55 of the opening angle of the lower jig.
Front and rear adjustment of the grinding rod
The front and rear adjustment of the grinding rod refers to the displacement of the center of the upper jig away from the center of the lower jig to the direction perpendicular to the swing. The displacement is 0-0.4 for the spherical surface.
Ratio of spindle speed to up swing speed
The faster the main shaft rotates, the more the edge of the lower jig will be ground, and the faster the upper swing speed will be, the more the center of the upper jig and the center of the lower jig will be ground. 1~2.5 times for spherical surface
Fifteen, ultrasonic cleaning principle
The principle of ultrasonic cleaning optical parts is mainly:
The cavitation effect of the ultrasonic field and the chemical action of the cleaning fluid. Surface contamination of optical components includes:
The dust accumulated in the air is not easy to remove due to electrostatic adsorption, and more solid particles are adhered to the surface by the oil film. The particles and the oil film may be organic substances or inorganic substances; The carbonized film layer formed; sometimes the parts also have an oxide film layer.
Put the polluted optical parts into the ultrasonic cleaning liquid, the ultrasonic vibration in the liquid, the alternating pressure produces alternating compression and loosening vibration motion, that is, cavitation phenomenon.
There are three cleaning effects:
- 1. The direct effect of strong ultrasonic waves on the polluted surface is to transfer the momentum from the moving liquid directly to the dirt medium particles, causing the particles to vibrate, and the particles with weak adhesion are detached from the surface. This is one of the cleaning effects of ultrasonic cavitation.
- 2. The polluted particles act as the nuclei of the cavitation phenomenon to promote the formation of the cavitation center, and the pressure changes rapidly to produce cavities filled with gas or steam, and the cavities of these cavities
- 3. The final collapse produces a strong shock wave, and its pressure increases by several orders of magnitude, which can break and separate the solid particles on the polluted surface. This is the second cleaning effect of cavitation.
- 4. The oil film adhering to the surface of the parts can be finely diffused in the liquid under the action of the ultrasonic cavitation phenomenon to form an emulsion, which is the third cleaning effect of the cavitation phenomenon.
The ability of the cleaning solution to dissolve the contaminated medium obviously also plays an important role. In the actual cleaning process, several cleaning effects occur simultaneously and alternately. In order to improve the cleaning quality, the power and frequency of the ultrasonic wave, the type of cleaning agent, the liquid temperature and the working process of the cleaning machine must be reasonably selected.
Factors Affecting Cleaning
1. The technical key of the cleaning process: whether the optical glass can reach the surface after cleaning without any oil stains, stains, smooth surface and intact water film!
2. Factors affecting the quality of glass after cleaning and corresponding solutions
- (1) The quality of the glass itself and its contamination are mainly: moldy spots, air bubbles, scratches, etc. on the surface. During mechanical processing, such as: grinding, wiping, and stress testing, the contamination caused by humans varies. ;
- (2) The choice of cleaning agent, its activity, temperature, and water quality; the most widely used cleaning agents in the world are CFC-113, carbon tetrachloride, 1-1-1 trichloroethane (ODS for short), etc. The agent is harmful to the ozone layer and is a non-environmental cleaning agent; we use a non-ODS water-based alkaline cleaning agent, which is mainly composed of water, alkali, surfactant, and anti-rust materials. It has a chemical formula of C3H8 and a cyclic olefin with side chains. , has a strong oil-dissolving ability; features: low toxicity, non-combustible, low cleaning cost, etc.;
- (3) The concentration of the solution directly affects the degree of cleaning;Usually the pH value of the cleaning solution is generally between 8.5-12. If the pH value is greater than 10, the effect of side surface active substances will be weakened. When the pH value is greater than 12, the side cleanliness will decrease. In actual use, it is found that when the concentration of the solution is too high, exceeding 15%, the cleaning effect is not good, and it is not easy to rinse, and when the concentration is about 4%-7%, the side cleaning effect is better.
- (4) The solution temperature and soaking time also affect the decontamination efficiency; when the temperature rises, the reaction speed of the solution also increases, and the viscosity of the pollutants decreases, which facilitates the removal of pollutants, but the stability of the solution decreases. It is actually found that the solution temperature is 50 degrees, and after soaking for 30 minutes, the cleaning effect is the best!The first one may be due to the water quality, the mist is like water traces; the dehydration is not perfect, it is not cleaned or the deionized water does not meet the requirements;The second one: it is because the ultrasonic tuning is too strong, it can be adjusted smaller or the fixture is unreasonable; it may also be caused by the frequency being too low. Generally, the ultrasonic frequency is above 40KHz, especially for thin ones. Glass sheet; if it is pure chemical cleaning time, if it is combined with ultrasonic cleaning, the cleaning time will be greatly reduced. Generally, the existing ultrasonic cleaning process is 5-8 minutes to produce a cleaning basket (about 15–30 pieces); if in If you use (4) for pre-soaking, the cleaning time will be shorter.
- (5) During the cleaning process, you should also pay attention to the need for pure water or deionized water. If you use hard water such as tap water, it is difficult to remove the oil stains on the glass, and impurities such as Ca and Na ions in the water will be lost after drying. A layer of white mist film is formed on the surface of the glass, polluting the glass;
- (6) The glass needs to be rinsed after cleaning. The cleanliness after rinsing is not only related to the rinsing of the detergent and the concentration of the detergent in the cleaning solution, but also to the number of rinsing processes, the amount of rinsing water supply, temperature and circulation. Is the pure water used clean?
- (7) Cleanliness of the cleaning environment
- (8) Drying process and temperature after cleaning: Keep the glass vertical as much as possible, and ceramic columns can be placed under the glass to avoid watermarks on the lower edge of the glass after drying; the oven temperature is controlled at about 70 degrees, and the time is about 20 minutes. If the temperature is too high, patterns will appear on the corners of the glass
Abnormal quality analysis steps
- 1. Whether the cutting appearance is rough, with patterns and knife marks
- 2. Whether the cutting arc is within the specification and whether there is an aspheric surface
- 3. Determine whether the ring diameter (diameter) is consistent, whether it is within the specification, and whether it is worn
- 4. Whether the first rough grinding can match the cutting radian, whether the radian after processing is within the specification, and whether the cut thickness is within the requirement
- 5. Whether the second rough grinding is compatible with the first (whether the third is coordinated with the second), whether the processed surface can meet the requirements of the subsequent process (whether the aperture is within the requirements)
- 6. How about the rough grinding pressure, will the appearance be better?
- 7. Will the aperture and appearance be better controlled if the fine grinding pressure is too high?
- 8. Whether the fine grinding swings and the pressure is uniform
- 9. Whether the grinding tank is clean, whether the grinding liquid is too thick or thin
- 10. Is the tripod loose (jumping)
- 11. Is there any difference in the thickness gauge, and whether the R value of the original device is within the specification?
- 12. Whether the radian of the repairing dish is within the specifications, whether the R value and other dimensions are within the requirements or whether there is wear
- 13. Is the lens off-center?
- 14. Whether the lenses are collected, rinsed and wiped clean in time, and whether the towels used are clean
- 15. Whether the heating time of the high-speed wire is reasonable, whether a thimble or a blade is used for stripping, and whether the tools used are sharp or sharp
- 16. Is the cleaning basket reasonable and will it be pinched?
- 17. Whether the criteria for judging have changed
- 18. Whether the raw material blank is deformed, whether the thickness is too thin, whether the chamfer is too large
The design of process regulations
- 1. Optical parts drawings, technical conditions, production equipment performance, etc. are the original materials that must be possessed in the design process regulations.
- 2. If the processing is a small-scale production, you can choose a block blank and adopt the elastic processing method; if it is mass production, you can choose a pressed blank and use a rigid processing method.
- 3. Determining the processing sequence must follow the principles of many, fast, economical and good. According to the blank type, part shape and technical requirements, technical level and production type, the main sequence is drawn up, generally as follows:
For spherical parts, the plane precedes the spherical surface; the concave surface precedes the convex surface; the larger radius of curvature precedes the spherical surface with a smaller curvature radius; cutting is to process the surface with smaller curvature first; the concave surface is processed first;